Although I would assume you were not thinking of spending $1000 (or more) on a trainer, if you wanted to lose nothing over the winter months, including your climbing fitness and indeed improve, get one of these;

It comes equipped with a power meter and when hooked to your PC it can replicate a ride you or someone else has ridden. Simply plug your favourite ride into the software and ride. As you follow on the map displaying on the PC, the resitance varies based on the terrain replicateing that exact ride indoors. You can also download (for free) other folks ride both with video and without. You can ride the world complete with video and acurrate resistance from your trainer. There is also the ability to write your own workout setting power levels and duration but riding the downloaded routes complete with videos would be the go to make it more enjoyable.

I personlly have not ridden one (but have used one for MAP tests) but would love one. Thing is here in Nth QLD we can ride year in and year out provided you don't mind the rain.

I use both... mag trainer for head down hard hit out, rollers for head down hard hit out ... I got just a hard work out on the rollers as the mag, just different thats all. I would still rather go outside for a ride in -15c than ride indoors... but when there really is no choice, well there really is no choice!.